A SHUNT REGULATOR FOR 150-kV, 20-A, 0.5-Sec NEUTRAL-BEAM-SOURCE POWER SUPPLIES*

The Lawrence Berkeley Laboratory (LBL) is now constructing a test facility for the development of neutral beam (NB) sources which will operate up to a level of 150 kV, 20 A, 0.5 sec with a 1% duty cycle [1]. Such sources will provide neutral deuterium beams for injection into large-scale experimental fusion devices. These sources require an accel power supply capable of wide-range variation, voltage regulation of ±1%, risetime ≤20 μsec, turnoff (crowbar) time of ≤10 μsec, repetitive crowbarring and restarting during a 0.5 sec pulse, and low rate of current increase during a short circuit. We describe a shunt regulator system which uses existing components and satisfies these requirements with simplicity and relatively low cost.